1. Field of the Invention
The present invention relates to a spark ignition type internal combustion engine.
2. Related Art
Known in the art is an ignition timing control system of an internal combustion engine which uses the engine operating state as the basis to calculate a base ignition timing, calculates a feedback correction value for correcting the base ignition timing so that the level of knocking which is detected by the knocking sensor becomes a target value, and corrects the base ignition timing by the feedback correction value and a learned value (see Japanese Patent Publication No. 2011-256725A). It is not preferable in control for the feedback correction value to steadily deviate from the reference value. Therefore, in Japanese Patent Publication No. 2011-256725A, the steady difference of the feedback correction value with respect to the reference value is set as the learned value and the base ignition timing is corrected by the feedback correction value and learned value. As a result, the feedback correction value is kept from steadily deviating from the reference value.
In Japanese Patent Publication No. 2011-256725A, the learned value is set in relation to the engine operating state which is determined by the engine load and the engine speed.